Hi all, I’ve got a 2001 xj sport, 3.2 V8 and the heating never works, always putting the heating on the high setting but it blows cold, even when the engine is at operating temperature, I’ve seen people say to look at the heating pump and valve but are they any ways to diagnose before throwing random parts at it lol
Any help is greatly appreciated
From a very cold man

 

The valve defaults to OPEN. (but could be stuck closed?)
The heater pump could be faulty? Put power to it and see if it works?
Heater matrix could be clogged?

 

hello, little bit new to this, what would you say is the best way to put power to the pump ? Just run two wires to the plug with a battery and listen for noise ?
thank you

 

Check for a blown fuse first.

If you have an ohm meter, unplug the heater pump and ohm test to see if the electric motor has continuity.

If you don’t have an ohm meter, start the engine up and put it on full heat. If you have a long screwdriver, put one end on the body of the electric pump and the other end up to your ear. You should hear something.

However, the impeller inside of that electric motor is NOT physically connected to the electric motor. It is driven by magnets. If you hear something like a little whirring noise, chances are the heater core is clogged. Do the simple test first and report back.

 

You can bang on the motor with a broom handle, and it will sometimes come loose and run

But not to hard as there are rubber mounts underneath that can break from old age

Same thing with hitting the solenoid

The repair of the motor is a pair of 3 buck brushes and depending on the hours of usage on the original motor not a bad idea to just go ahead and replace the brushes

I have some extra brushes

You can put your finger on the solenoid and feel for it to click open with a cold cabin temperature , a warm cabin it will remain closed and not modulate open

But the electric motor should run at all times with the heat selected

Fuse ?

You can run the motor with a battery charger and there will be a high current arcing hazard but otherwise the motor has internal resistance so no shorting out the motor

Try the charger on 2 amps first and not 50

The motor will jump out of your hand like fish out of water

To know if the solenoid as working open at high engine RPMs there will be some heater core water flow and heating on the inline 6 engine

But in the V8 there is a check valve added that may prevent this along with some other reasons

 

Fuse

 

I've been researching heater issues in the archives and saw a post that said to set heat to "HI" and run engine at over 2000rpm. The flow from the water pump at > 2krpm will drive some heated coolant through a clear heater matrix even if the pump isn't working and you'll feel the heat.

If you do get significantly more heat at >2krpm then the aux pump isn't doing it's job so check fuse/relay and then check aux pump bushes.
Pump removal Here. Brush replacement instructions Here.

If you don't get more heat then the valve isn't working correctly or the heater matrix is blocked. Try flushing the matrix before replacing the valve.

I've been getting minimal but some heat regardless of engine revs so seems like the pump may be working. I can also hear it whirring. I'm thinking the valve may be stuck partially open which would explain why I also get AC that's not cold enough in the summer when it should be closed. I'm thinking of flushing the matrix and if no change checking then changing the valve.

This is on a low miles Florida car that probably never needed much heat so the valve won't be moving much. I had a Florida XJ40 that had a stuck blend flap. This seems a lot like that situation, both AC and heat improved once the blend flap was moving. On the X308 seems like the valve does the same job as a blend flap.

 

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